Designing a Second Order Passive LPF: Tips and Insights

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SUMMARY

The discussion centers on the design of a second-order passive low-pass filter (LPF) and the challenges faced when attempting to achieve the correct cutoff frequency. The user initially attempted to cascade two RC circuits and used the formula 1/(2πRC) for cutoff frequency calculation, but found discrepancies in simulation results. A suggestion was made to consider active filters using operational amplifiers (op-amps) instead, referencing the book "Digital Signal Processing" by Steven Smith for further guidance on analog filters.

PREREQUISITES
  • Understanding of RC circuit design
  • Familiarity with filter design concepts
  • Knowledge of operational amplifiers (op-amps)
  • Basic simulation software for circuit analysis
NEXT STEPS
  • Study the design principles of second-order passive low-pass filters
  • Explore active filter design techniques using operational amplifiers
  • Read "Digital Signal Processing" by Steven Smith, focusing on analog filters
  • Learn about simulation tools for circuit design and analysis
USEFUL FOR

Electronics students, hobbyists designing filters, and engineers involved in analog circuit design will benefit from this discussion.

ACLerok
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This isn't really an exact homework problem since it's for a report I'm doing. Basically, I was wondering what the design for a second order passive low pass filter looks like. I know how to design a regular first order circuit but I have no clue about a second-order PASSIVE LPF. I tried just cascading two RC circuits and using 1/(2pi(RC)) to define the cutoff frequency but after simulating it on my computer, the actual cutoff is quite off. Anyone have any insight into this?? Thanks in advance.
 
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Why do you want to make a passive filter? Take my advice and use an active filter. The techniques for making active filters using op amps is very mature and you can get whatever gain you wish. Look for the book on the web (its free!): "Digital Signal Processing" by Steven Smith. Look on page 50 for a good discussion on analog filters and a simple design table.
 
Believe me, I would, but it tells me to make a 2nd order passive LPF in the assignment. Thanks though.
 
Shame there was no answer to this forum :( I am stuck now too I have to do a 3rd order high pass RC active filter though
 

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